1. Field of the Invention
The present invention relates to a method of manufacturing a substrate for liquid ejection head to be used for a liquid ejection head which ejects liquid such as ink liquid.
2. Description of the Related Art
In recent years, in an ink jet recording head, increase in the number of ink supply ports and narrowing of pitches between the ink supply ports have been progressing. In this trend, it is required to surely secure an adhering area between a rear surface of a substrate of an ink jet recording head provided with supply ports and a support member for supporting the ink jet recording head, to thereby maintain an adhering strength. Therefore, in order to maintain the adhering area, it is desired to reduce fluctuations in shape of the ink supply ports. However, in some cases, an opening accuracy of the ink supply port reduces because of flaws and defects in a silicon substrate, flaws in an etching mask, and the like.
To address this, in Japanese Patent Application Laid-Open No. 2007-160625, there is proposed a method of forming a protective layer as an etching mask after forming a functional portion formed of a flow path forming member and the like and before forming the ink supply port, the protective layer being formed by low temperature sputtering after grinding or polishing the rear surface of the substrate to eliminate the flaws.
However, in the substrate subjected to grinding or polishing to eliminate the defect portion, due to the grinding or the polishing, an etching rate (side etching rate) progressed in a surface direction of the substrate fluctuates. In this case, it is possible to improve the accuracy, but it becomes difficult to form the opening correspondingly to the etching mask.